Free flow acoustic silencer constructed of resilient material



June 8, 1965 c. G. BEECHING 3,187,837

FREE FLOW ACOUSTIC SILENCER CONSTRUCTED OF RESILIENT MATERIAL Filed Aug.28, 1965 3 Sheets-Sheet l 26 l5 I6 I I0 25 mun/roe CHARLES G. BEECH INGMATERIAL June 8, 1965 c. G. BEECHING FREE FLOW ACOUSTIC SILENCERCONSTRUCTED OF RESILIENT Filed Aug. 28, 1963 June 8, 1965 c. e. BEECHINGFREE FLOW ACOUSTIC SILENCER CONSTRUCTED OF RESILIENT MATERIAL Filed Aug.28, 1963 3 Sheets-Sheet 5 United States Patent Canada) Filed Aug. 23,1%3, No. 3ll5,234

9 Claims. or. ran-es This invention relates to silencers or mufi'llersused to reduce the exhaust noise of internal combustion engines, and hasparticular reference to inboard marine installations, and to stationaryinstallations.

This application is a continuation-in-part of my prior copendingapplication, Serial No. 13,070, filed March 7, 1960, now abandoned.

It is possible by conventional means greatly to reduce exhaust noise. Ifsilencing is by means of baliie plates, flaps, slits, and like devices,in mufflers of ordinary size having regard to the power of the motor,back pressure results. This causes material loss of power, rapid burningof exhaust valves, fouling, and other undesirable effects. With largermufiiers, the undesirable effects are reduced but the expense isconsiderable. In either case, the useful life before replacement orrepair may be short.

The objects of the invention are to produce a silencing device of cheaplight construction which shall be free of the defects above.

in my mufiler silencing is accomplished by acoustic damping chambers,and it is provided that the exhaust gases flow sensibly unimpededthrough the device, encountering only resistance of the order of that ofthe exhaust pipe itself. The design is adapted to cheap light massproduction in natural or synthetic rubber, resilient plastic, or likematerial, non-corrosive, resistant to oil acid and the like, and havingadequate heat-resistant properties. Construction in such materials isparticularly suitable to marine installations where cooling water isdischarged through the exhaust.

Other objects, advantages and details of the invention will be apparentas the description proceeds, reference being had to the accompanyingdrawings wherein several forms of the invention are shown. It is to beunderstood that the description and drawin s are illustrative only, andthat the scope of the invention is to be measured by the appendedclaims.

In the drawings:

FIG. 1 is a side elevational view of one form of muffler embodying theinvention.

FlG. 2 is a longitudinal sectional view of the muiiler shown in FIG. 1,the view taken on line A-A of FIG. 3.

FIG. 3 is an end elevational view of the muiller shown in FIGS. 1 and 2.

FIG. 4 is a side elevational View of a commercial mufiler embodying theinvention.

FIG. 5 is a longitudinal sectional View of the muificr shown in FIG. 4,the view taken on line 5-5 of PEG. 6.

FIG. 6 is a transverse sectional view taken on line 6-6 of FIG. 4.

FIG. 7 is a longitudinal sectional view of another commercial mufflerembodying the invention, the view taken on line 77 of FIG. 8.

FIG. 8 is a transverse sectional view taken on line 3-8 of FIG. 7.

In FIG. 1 the hollow body or shell indicated by the numeral 1 consistsof the parts 2 and to be vulcanized or cemented at the joint ir In theembodiment now being described, the mufiler is constructed of plasticmaterial, or of suitable natural or synthetic rubber.

The shell end walls 5 and 10 contain parts 29 and 36 generally 3 adaptedadapted as shown to receive the exhaust pipe 6 and the tail pipe 7respectively. Exhaust pipe 6 connects directly to the exhaust manifoldof the internal combustion engine (not shown), and is of standarddiameter as supplied or recommended by the manufacturer of the engine.The tail pipe '7 preferably may be somewhat larger than the exhaust pipeaforesaid. The parts 29 and 30 are aligned as shown.

The muflier is secured to the exhaust and tail pipes by conventionalclamps 8 and 9. It will be understood that the tail pipe merely servesto lead the exhaust gases from the muffler to a suitable dischargepoint, and has no material effect upon the operation.

As shown in FIG. 2, the shell end walls 5 and 10 have shoulders formedat 11 and 12. Pieces l3, 14, 15, 16 and 26 are hollow cylinders ofprogressively diminishing length.

17 through 2d are partitions transverse of the length of the mufflershell 1 dividing the same internally into acoustic damping chambers 21,through 25. Referring to the partition 17, this is of disc shape havingdiameter equal to the inner diameter of the shell 1, less a suitablesmall clearance to facilitate assembly. It contains the opening 2'7,suitably circular, the area of which opening is not less than that ofthe inner diameter of the intake pipe e, or tail pipe '7, whichever maybe greater. The opening 27 is disposed opposite the intake port 29 asshown. The succeeding partitions l 19, 20 are the same as, andinterchangeable with, the partition 17, and the openings are aligned asshown.

Assembly is as follows. Cylinder 13 is inserted in the hollow shellportion 3 to bear against the shoulder 11 of the end wall in, and thedisc 1'7 placed in position as shown in FIG. 2. Next the cylinder 14 isplaced in position completing the assembly of the left hand portion 3 ofthe silencer. These parts are cemented or vucanized to one another.

In like manner, cylinder disc 20, cylinder 16 disc 3%, cylinder 15 disc18, are progressively inserted in the right hand portion 2 of the shell1, and cemented or vulcanized to form the right hand portion of themuffler.

The two completed sections are joined by inserting cylinder 14 into oneportion, and sliding the other portion over that part of 1 5 nowprotruding, to form the joint 4, the whole being suitably vulcanized orcemented together.

it is seen that the mufder consists of the several chambers 21 through25 of diminishing size, communicating by means of openings as 27.

The action is described with reference to FIG. 2. EX- haust gases flowin the manner indicated by the arrows, and it is seen that there isclear space, circular in section, throughout the length of the mulfier,the least diameter of which clear space is not less than the greater ofthe inside diameters of the exhaust pipe 6 or tail pipe 7.

Thus the mean pressure within my mufller will be less than thecorresponding mean pressure in that part of the exhaust pipe immediatelypreceding the muffler; accordingly freedom from burned out exhaustvalves, fouling and like effects will be as in an unmuliled engine withan open exhaust pipe. As well, the power will not be re duced fromexcessive back pressure.

The pressure in exhaust pipe d is pulsating violently, at frequencyaccording to the explosions of the cylinders of the internal combustionengine. Superimposed upon this primary wave are complex audibletransients. The complex entering pressure wave expands into chamber 21,and the lower frequencies and their harmonics tend to be damped. As thedischarge proceeds from chamber to chamber higher frequencies areabsorbed in a similar manner by the succeeding chambers of diminishingsize. The result is that most of the audible frequencies have proarenas?gressively been damped, and while the discharge will still pulsate inpressure, the amplitude of the pulsation s materialiy reduced and, withit, the noise.

Silencing to an extent, will take place when exhaust gases are permittedto expand into a hollow shell, or enlarged exhaust pipe portion, withoutbathing. When apertured baffles are added, still further silencingoccurs. The rnufiling action increases when the battles are transverseported'partitions so spaced to define acoustic chambers as described.

The device described above employs a pliable resilient shell which, incombination with the above features, provides further damping. It isapparent that the pulsations of pressure within this shell are large,and consequently there is deformation of the shell, and difficulty inproviding attachment of the baffies to the shell without making theshell of undue thickness, and consequentlyot rigidity such as to impairflexibility. This diificulty I have overcome in the manner abovedescribed, namely by providing cylindrical spacers separating thebaffles. As will be clear from FIG. 2, this arrangement acts to form acomposite shell composed of the outer part, and the inner spacingcylinders as 15. In this way I am able to provide a composite ofsuitable total wall thickness. Moreover, manufacture and assembly arethereby facilitated.

Using this construction, and with total thickness of the composite wallas small as three sixteenths of an inch, I am able to make a compositeshell sufiiciently thin to have the required flexibility and, at thesame time, I overcome the difficulty of rigid attachment of thepartitions, or baffles, to the wall.

PlGS. 4-6 shows one commercial form of mufller embodying the invention.The respective component parts are molded from suitable resilientmaterial, such as natural or synthetic rubber, that is non-corrosive,resistant to oil, acid and the like, and has adequate thermalproperties.

Outer shell 35, as illustrated, is formed from two like parts 36 and 37,the two parts being cup-shaped and provided at their open ends withflanges 38 and 39 adapted to be secured together in final assembly. Endwalls dill and 41 of parts 36 and 37 have central circular ports 4-2 and43, the ports being surrounded on the external faces of the walls bytubular portions 44 and 45 adapted to be connected respectively toexhaust and tail pipes (not shown).

Referring to FIGS. and 6, a plurality of chamberforming units ofresilient material are disposed within shell 35. The chamber-formingunits vary in size, and so will be described separately. Each unit iscup-shaped, as will be seen.

Chamber-forming unit Sti is located at the left-hand end muffleradjacent end wall 469 having a port d2 that admits exhaust gases to themufiler interior. 7

Unit 50 has a bottom portion 51 that serves as a transverse partitionwithin shell 35 and a side wall 52 that serves as a spacer determiningthe axial length of chamber 53- formed by the unit. Bottom portion 51,best shown in FIG. 6, has an elongated opening 54, the shape of opening54 in the illustrated embodiment being substantially oyal. The majoraxis of opening 54 is shown about equal in length to the diameter ofbottom portion 51, although it may be somewhat shorter.

The area of the opening 54 is not less than the greater of the areas ofports 42 and 43 in the end walls of outer of the muffier shown in FIGS.4 and 5, the end of the 7 shell 35, the areas of such ports usuallybeing about the I same size.

Proceeding to the right, next adjacent chamber-forming unit 55 hasbottom portion 56 and side wall 57, the length of side wall 57 beingsuch that the over-all axial length of defined chamber 58 is somewhatless than that' of chamber 53. As shown, the length of side wall 57 issubstantially equal to that of side wall 52; however, the axial lengthof larger chamber 53 is the distance between opening 42 and bottomportion 51. Thus, the same sized unit may be used for both chambers.

Bottom portion 56 of unit 55 has an opening 59 of substantially the sameshape and size as opening 54- in preceding bottom portion 51, As will beseen, opening 59 preferably has aditlerent angular orientation thanopening 54-.

Next adjacent chamber-forming unit 6h has bottom portion 61 and sidewall 62, the latter having such length that defined chamber 63 has asmaller axial length than preceding chamber 58. Side wall 62, as shown,projects to the right beyond bottom portion 61, as shown at 62a, theextending portion serving as a spacer with respect to end wall 41 of theouter shell. 7

Bottom portion 61. of unit 6! has an elongated opening 64 ofsubstantially the same size and shape as the previous openings 54.- and59. The three openings are shown in superimposed relation in FIG. 6.

As shown in FIG. 6, the respective chamber-forming units 56, 55 and 6bin the illustrated commercial form are angularly oriented so that themajor axes of the openings 59 and 6d dilfer from the major axis of thepreceding openings by a predetermined angle. The angle illustrated issubstantially sixty degrees. Thus, the majoraxis of opening 54 is showndisposed vertically, the axis of open ing 5) is disposed sixty degreesclockwise therefrom, and the axis of opening 64 is disposed sixtydegrees clockwise from the axis of opening 59. It has been found thatthese angular orientations impart a rotary movement to gases passingthrough the muflier, and such rotary movement increases the effectivelength and the silencing quality of the muffler, and avoidsobjectionable back pressure.

In the commercial muffler described above, the outer diameter of shell35 is six inches, and the respective axial lengths of the chambers 53,58, 63 and rigl1t-hand chamber as are four inches, three inches, two andone-half inches and two inches. The diameter of end ports 42 and 43 issubstantially three and one-eighth inches.

it has been found that a mufiier constructed to these dimensions ishighly elfective from the standpoint of silencing and the prevention ofobjectionable back pressure.

FIGS. 7 and 8 illustrate another commercial embodiment of the invention,this form differing from the FIGS. 4-6 form only in the angularorientation of the respective chambenforrning units 70, 71 and '72.Here, the major axes of the elongated openings in the bottom portions ofthe units differ in orientation from that of the major axis of thepreceding opening by ninety degrees. Thus, as shown, opening '73 in unit7% has its major axis oriented vertically, and the major axis offollowing opening 74- is oriented ninety degrees clockwise, orhorizontally. Opening 75 in unit 72 has its major axis oriented ninetydegrees farther in clockwise direction, or vertically, the same as theaxis of the first opening 7'3.

It is believed that the relative orientations of the openings shown inFIGS. 7 and 8 cooperate to impart an oscillating movement to the gasespassing through the muftier. Such movement, as in the case of the rotarymovement provided by the sixty degree differential, increases theeffective length and silencing quality of the mufiler, and avoidsobjectionable back pressure.

Experimentation has shown that desirable results are achieved withangular differentials falling in the range of from one to ninetydegrees.

From the above description it is thought that the construction andadvantages of this invention will be readily apparent to those skilledin the art. Various changes in detail may be made without departing fromthe spirit or losing the advantages of the invention.

Having thus described the invention, what is claimed as new and desiredto secure by Letters Patent is:

ll. A silencing device for attachment to the exhaust pipe of an internalcombustion engine comprising:

an outer resilient shell of substantially uniform cross section having aside wall and end walls, one end ing an opening of substantially ovalshape, the major wall ported and adapted for connection to the exaxis ofsaid opening substantially equal in length to haust pipe aforesaid, theother end wall ported and the diameter of said bottom portion and thearea of adapted for the connection of a tail pipe for egress saidopening not less than the greater of the areas of exhaust gases, theshell fabricated in two parts of said ports in said shell end walls; tofacilitate assembly, said two parts having open said chamber-formingunits oriented in said shell so ends adapted to be joined afterassembly, the angular position of the major axes of said oval transversepartitions within the shell to define chambers openings in successivechamber-forming units after of unequal size the largest said chamberbeing that the unit nearest the gas-admitting end wall diiters adjacentthe end wall ported for the exhaust pipe from the angular position ofthe major axis of the as aforesaid, an opening in each said partition,each preceding oval opening by a predetermined angle. said openinghaving an area not less than the greater 4. The combination of claim 3wherein said predeterof the internal diameters of the said exhaust andtail mined angle is substantially sixty degrees. pipes, the saidopenings aligned With one another 5. The combination of claim 3 whereinsaid predeterand with the end wall ports, mined angle is substantiallyninety degrees. cylindrical spacers, of resilient material similar tothat 6. The combination of claim 3 wherein said predeterof the outerresilient shell, for insertion within the mined angle falls in the rangeof from one to ninety outer resilient shell, the outside diameters ofsaid degrees. spacers equal to the inside diameter of the outer shell,'7. A silencing device for attachment to the exhaust the axial length ofthe spacers such as to define the pipe of an internal combustion enginecomprising: distance between said transverse partitions, an outerresilient shell having a side wall and opposite the outer resilientshell and the resilient spacers aforeend walls, one end wall having aport to admit exsaid comprising a composite shell of total thicknesshaust gases and the other end wall having a port to not less than threesixteenths of an inch. discharge said gases; 2. A silencing device forattachment to the exhau t chamber-orming units of resilient materialwithin said pipe of an internal combustion engine comprising: shelldefining chambers of progressively smaller size, an outer resilientshell having a side Wall and opposite the largest of said chambers beingadjacent said gasend walls, one end wall having a central circular portadmitting end wall, each chamber-forming unit cupto admit exhaust gasesand the other end wall having shaped with the bottom portion thereofconstituting a central circular port to discharge said gases, said apartition separating adjacent chambers and the side shell fabricated intwo parts to facilitate assembly, wall thereof constituting a spacerdetermining the said two parts having open ends adapted to be joinedaxial length of the chamber formed by said unit, together; said sidewall of said unit engaging the side wall of chamber-forming units ofresilient material within said said shell;

shell defining chambers of progressively smaller size, the bottomportion of each chamber-forming unit havthe largest of said chambersbeing adjacent said gasing an elongated opening, the major axis of saidopenadmitting end wall, each chamber-forming unit cupin substantiallyequal in length to the diameter of shaped with the bottom portionthereof constituting said bottom portion and the area of said openingnot a partition separating adjacent chambers and the side less than thegreater of the areas of said ports in said wall thereof constituting aspacer determining the shell end Walls; axial length of the chamberformed by said unit, said chamber-forming units oriented in said shellso said side wall of said unit secured to the side wall thh angularPOShiOh 0f the major flXeS 0f Said @1011- of said shell; gated openingsin successive chamber-forming units the bottom portion of eachchamber-forming unit havafhir the unit nearest the gas-admitting andW311 ing an opening of substantially oval shape, the major fers from theangular Position of the major s f axis of said opening substantiallyequal in length to The Pracedihg elongated Opening y a predetermined thediameter of said bottom portion and the area of g said opening not lessthan the greater of the areas of A Sikh-ling (lei/1'66 for attachment t0the eXhauSt areas of said ports in said shell end walls; pipe of aninternal combustion engine comprising: said chambenforming unitsoriented in aid hell so an outer resilient shell having a side wall andopposite the angular position of the major axes of said oval 611d Walls,0116 end Wall having a P to admit openings in successive chamber-formingunits after hflhst gases and the other end wall having a P t0 the unitnearest the gas-admitting end Wall differs discharge Said and from theangular position of the major axis of the Chamber-forming units ofresilient material within said preceding oval opening by a predeterminedangle, shell defining chambers of progressively smaller size, wherebyrotary motion is imparted to exhaust gases the largest of Said Chambersbeing adlacfiht Said passing through said device to thereby increase thethis-admitting end W311, each Chamber-forming llhl't effective lengthand silencing quality of said device. P- p With the bottom PortionThereof 3. A silencing device for attachment to the exhaust Stithtihgaphrtlfioh Separating adjacent Chambers and ipe of an internalcombustion engine comprising; 60 the side wall thereof constituting aspacer determinan outer resilient shell having a side wall and opposites the aXial lihglh 0f the Chamber foimed y Said end walls, one end wallhavin a port t d it unit, said side wall of said unit engaging the sidewall haust gases and the other end wall having a port to of said shell,the bottom portion of each chamberdischarge said gases; forming unithaving an elongated opening, the major chamber-forming units ofresilient material within said axis of said Opening Substantially equalhi length t0 shell defining chambers of progressively smaller size, [116diameter of said bottom 130M011 and the a f the largest of aid ha b b idj i said opening not less than the greater of the areas ofgas-admitting end wall, each chamber-forming unit Said Ports in SaidShell and Wallscup-shaped with th b tt ti th f h 9. A silencing devicefor attachment to the exhaust stituting a partition separating adjacentchambers and P p of all internal Chmbusfion engine comprising! the sidewall thereof o tit ti a spacer d i an outer resilient shell having aside wall and at least ing the axial length of the chamber formed bysaid one and Wall having aP0rt therfiih; and unit, said side wall ofsaid unit engaging the ide chamber-forming units of resilient materialwithin said wall of said shell; shell defining chambers of progressivelysmaller size,

the, bottom portion of each chamber-forming unit haveach chamber-formingunit cup-shaped with the bottom portion thereof constituting a partitionsepa- 1,769,778 7/30 Field 55-419 rating adjacent chambers and the sideWall thereof 1,769,778 7/30 Field 5519 constituting a spacer determiningthe axial length 1,874,326 8/32 Mason 181-47 of the chamber formed bysaid unit, said side wall 1,990,837 2/35 Morgenstern 18161 X of saidunit secured to the side Wall of said shell, the r, 2,238,316 4/41 M i t181 59 bottom portion of each chamber-forming unit having 2 77 3 0 3/59H fif 181 5Q an elongated opening, the major axis of said openingsubstantially equal in length to the diameter of said FOREIGN PATENTSbottom portion and the area of said opening not less 116,283 2/30Austrizh than the area Oi. said port in said shell end wall. 101,116,944 2/56 France References Cited by the Examiner 303,895 2/59Great Br UNITED STATES PATENTS 470,904 4/52 1,274,943 8/18 Schmidt 18156LEO SMILOW, Primary Examiner.

1. A SILENCING DEVICE FOR ATTACHMENT TO THE EXHAUST PIPE OF AN INTERNALCOMBUSTION ENGINE COMPRISING: AN OUTER RESILIENT SHELL OF SUBSTANTIALLYUNIFORM CROSS SECTION HAVING A SIDE WALL AND END WALLS, ONE END WALLPORTED AND ADAPTED FOR CONNECTION TO THE EXHAUST PIPE AFORESAID, THEOTHER END WALL PORTED AND ADAPTED FOR THE CONNECTION OF A TAIL PIPE FOREGRESS OF EXHAUST GASES, THE SHELL FABRICATED IN TWO PARTS TO FACILITATEASSEMBLY, SAID TWO PARTS HAVING OPEN ENDS ADAPTED TO BE JOINED AFTERASSEMBLY, TRANSVERSE PARTITIONS WITHIN THE SHELL TO DEFINE CHAMBERS OFUNEQUAL SIZE THE LARGEST SAID CHAMBER BEING THAT ADJACENT THE END WALLPORTED FOR THE EXHAUST PIPE AS AFORESAID, AN OPENING IN EACH SAIDPARTITION, EACH SAID OPENING HAVING AN AREA NOT LESS THAN THE GREATER OFTHE INTERNAL DIAMETERS OF THE SAID EXHAUST AND TAIL PIPES, THE SAIDOPENINGS ALIGNED WITH ONE ANOTHER AND WITH THE END WALL PORTS,CYLINDRICAL SPACERS, OF RESILIENT MATERIAL SIMILAR TO THAT OF THE OUTERRESILIENT SHELL, FOR INSERTION WITHIN THE OUTER RESILIENT SHELL, THEOUTSIDE DIAMETERS OF SAID SPACERS EQUAL TO THE INSIDE DIAMETER OF THEOUTER SHELL, THE AXIAL LENGTH OF THE SPACERS SUCH AS TO DEFINE THEDISTANCE BETWEEN SAID TRANSVERSE PARTITIONS, THE OUTER RESILIENT SHELLAND THE RESILIENT SPACERS AFORESAID COMPRISING A COMPOSITE SHELL OFTOTAL THICKNESS NOT LESS THAN THREE SIXTEENTHS OF AN INCH.